Portable arm rest



FIG. 1 is a front perspective view of a portable arm rest, showing my new design;

FIG. 2 is a top plan view thereof;

FIG. 3 is a left side elevational view thereof;

FIG. 4 is a right side elevational view thereof; and,

FIG. 5 is a rear elevational view thereof. 

The ornamental design for a portable arm rest, as shown. 